Chemistry 2A Week 6 Review

     This week in Chemistry was a pretty busy one. With multiple experiments and the celebration of mole day, week 6 in Chemistry 2A was a fun one.
     On Monday we started things off with Dr. Finnan showing us the power of the tesla coil. I thought it was really neat how we could actually see the electric current traveling through the air.

 

     Dr. Finnan showing us the tesla coil

 

 

      On Monday we also learned about Thomson's model of the atom, plum pudding. Plum pudding is described as thousands of negatively charged corpuscles that swarm inside a sort of cloud of mass less positive charge. Thomson came to this conclusion through a series of experiments. In his first, he discovered that when he bent a cathode ray (charges of negative electricity carried by particles of matter) with a magnet, not as much negative charge came through. In his second experiment, he realized that charged particles will normally curve as the move through an electric field, but if it's surrounded by a conductor, this won't happen. In his final experiment, Thomson found out that the mass-to-charge ratio for cathode rays turned out to be far smaller than that of a charged Hydrogen atom.
     Thomson's experiments challenged the ideas that scientists believed about electricity. His experiments were ground breaking and opened up many new opportunities for research on electricity and charge.
     On Tuesday, we conducted the sticky tap lab. We charged up pieces of tape, the top and bottom, and tested to see what they attracted.
     Sticky tap lab setup

    At the end of the lab, we discovered that opposite charges attract, neutral attract with positive and negative but not other neutrals, and that positive on positive and negative on negative repel. Through this experiment we furthered our understanding on charges and discovered how they attract each other. In addition, through the Sticky Tape Post-Lab Worksheet, we discovered that electrons can move through metal objects, and cannot move through non-metal objects, but rather shift over to avoid the charge being applied.
Picture of our diagram explain how electrons can move through metals

 Also, I understand our conclusions we got from this lab.
     On Wednesday, we conducted the conductivity lab. We tested the conductivity of many different materials and recorded data in our notebooks.
Example of conductivity testing station

     After we tested everything, the class tried to categorize what was conductive and what wasn't. This I had trouble with. Through class discussion, I began to understand it. Conductors conduct because of little resistance to the flow of charge that goes through them. Metals allow electrons to move through them while ionic conductors allow free ions (charged atoms) to flow freely.
This whiteboard answered many of the questions I had about categorizing conductors.

I believe I have a pretty solid understanding of categorizing conductors. The key is that a conductor must give little resistance to the flow of charge.   
     On Thursday, we began the Electrolysis of CuCl2 (aq) lab and recorded data in our notebooks. When we plugged in the cables, we discovered the positive side began to bubble and smell like chlorine. There was no smell and no bubbles on the negative side. Later in the hour, w checked up on the experiment and found that the graphite on the negative side began to turn pink at the bottom. We waited until Friday to see the final results of the experiment.
     On Friday, we revisited the experiment, and found the following images.

 

 We concluded that copper was on the negative side and chlorine on the positive side. The electrons were traveling through the graphite, not the water. The copper ions were being converted into neutral metal, hence the pinkish brown trail beneath the graphite.
Example of white-boarded conclusions

 I sort of understand these conclusions. I get that electrons can't travel through water but I still don't really understand why the copper ions are being converted into neutral metal. Is it because copper and chloride ions break up in water?
   On Friday we continued work with Unit 6 Worksheet 1. I understood how to draw the particle diagrams for all the compounds given. The 3+ and 3- stuff confused me. I get that each compound has to be neutral. Like Ga2O3 is Ga+3, Ga+3 and O-2, O-2, O-2. It's Ga+6, O-6. Those add up to be zero, I get that. What I don't understand is how we found Ga+3 and O-2 in the first place. I hope to find out more next week and I will ask questions so I better understand this concept.
   Other that the confusion on Friday, this was a good week. The class got a lot done and I was attentive through most of class. I hope to clear my view and better understand Friday's concepts.
     Also thank you to Mrs. Finnan for the cookies!! They were really good and looked adorable.

 

 

Chemistry 2A Week 5 Review

    This week in chemistry was not too eventful. We spent much of the week reviewing for the Unit 5 Test on Friday, which I'm pretty sure I did a-mole-zing on.

     On Monday we took a short quiz that tested us on conversion skills. We had to go from grams to moles, moles to grams, and moles to atoms. I got 8/8 on the quiz and I understood it. I just messed up on significant figures. I don't understand sig figs at all, I just focused on doing the work right.
Unit 5 Quiz 1c

 

     On Tuesday we completed Unit 5 worksheet 3. We learned the difference between empirical and molecular formulas. Empirical are experimental based while molecular is exact and based on the actual number of atoms in each compound. When given the molar mass, you find the empirical formula and adjust according to what the molar mass is. Like in problem 4 of worksheet 3. We find the empirical formula to be HO. However, we have a molecular mass of 34 g/mol. So you take the atomic mass of Oxygen, 16, and since there is only one Oxygen in the empirical formula, you add 16 to the atomic mass of one Hydrogen, which is 1. If the empirical would have been H2O2 the we would have done 16x2 + 2x1 because of the number of atoms in the empirical formula.

     Anyways, we take 34, our molar mass, and divide it by 17 (H+O). This equals two. So now the molecular formula is H2O2 because the molar mass divided by the atomic mass sum is two. I understood this after some practice with worksheet 3. Explaining and discussing with my table mates helped me get a better understanding of this.

Unit 5 worksheet 3



 

 

     On Wednesday we had PSAT testing and didn't do anything in class.

 

     We spent all of Thursday doing the unit 5 review. There were some things I didn't remember, like relative mass, but now I remember after doing the review. For relative mass, you just divide all your data by the smallest number you got. The data is relative to the smaller number.

     The review also included more conversions, and more problems with empirical and molecular formulas. I felt prepared for Friday's test.

Problems from review guide

 

     On Friday we took the Unit 5 test. I thought it went pretty well. There were probably some stupid mistakes I made but I knew what the questions were asking. I still have no idea about sig figs. I didn't pay attention to them on the test.

 

     Overall I thought it was a good week. We reviewed a lot which really helped. I look forward to seeing what I got on my test!!

 

 

P.S.-What is Avogadro's favorite holiday??

 

 

Cinco de Mole-o!!



Chemistry 2A Week 4 Review

     This week in chemistry most of what we did revolved around the mole. At first, many, including myself, had a hard time understanding what a mole was. But, through worksheets and continuous setup of conversions, I discovered the mole is simply a number. 6.02E23. I can have a mole of pencils if I have 6.02E23 pencils. I can have a mole of chicken wings if I had 6.02E23 chicken wings. A mole is just a number.

     On Monday we completed the Relative Mass and the Mole worksheet. By comparing chicken and quail eggs we slowly began to figure out what a mole was. I remember early on in the week I struggled with this concept. I kept making the problems more complicated than what they had to be. Dr. Finnan taught us the conversion method. We used this on many of our worksheets including the extension to the Relative mass and the Mole worksheet. The conversion method makes finding moles a lot easier.

     Example of conversion method

     On Tuesday we continued to learn about the mole with the Chemistry Unit 5-The Mole worksheet. The worksheet gave us nice examples of moles so we could grasp the concept of the mole as a number. For example, if we had a mole of rice grains, all the land area of the earth would be covered with rice to a depth of about 75 meters. The class continued to practice the conversion method with this worksheet and I myself understood the mole a lot better after Tuesday's work.

     On Wednesday we began the Empirical Formula Lab. First we received a beaker and we measured the beaker. We then added zinc and measured the mass of the beaker and zinc. After we found both weights using the scales, we added about 50 mL of  3M HCl. The beaker began bubbling and fizzing. We then put our beakers under the hood and waited until Thursday so we could see what had happened to our zinc.

     On Thursday, we continued the Empirical Formula Lab. We took our beakers back from under the hood and measured the mass of the beaker and its contents again. The mass had gone up compared to Wednesday's measurement. We then burned the zinc chloride. While burning, a funny smell was produced and the color of zinc chloride went from white to brown. We then measure the mass of the beaker and its contents again and found a slight decrease in mass compared to the measurement we took before burning it. After all the measuring, we completed the back side of the worksheet and found the empirical formula for zinc chloride to be ZnCl2. This makes sense to me because from our calculations, we know there are about twice as many moles of Cl than moles of Zn.

Empirical Formula Lab Class Data

 

 

Burning of the zinc chloride

Table 5 having fun in Chemistry 2A!!

 



 

     On Friday the class finished a good week of moles with the Unit 5 Worksheet 2 in class and homework. The in class part went alright. I don't think the entire class understands the concept of the mole. There were problems when the class was white-boarding that didn't really make sense. Some groups did a good job and some didn't.

    As for me, I have a pretty solid concept of the mole and the conversion method of calculations. The one part I don't really understand is when a problem asks you to find the number of atoms of a specific element in a compound. Like number 9 on the homework. I might be making it too complicated but I hope to clarify it next week in class. My participation was pretty good overall. I could definitely be more focused in class. Other than that I look forward to another exciting week in Chemistry 2A.

Chemistry 2A Week 3 Reveiw

On Monday, the class continued to review for the test that was originally supposed to be on Tuesday, but got changed to Wednesday. We white-boarded Unit 4-Describing Substance Objectives and reviewed items such as properties of matter. Pure substances are single elements or compounds. Elements are one or more of a single type of atom while compounds are two or more different types of atoms chemically bonded together. A mixture is a mix of different elements and/or compounds. Also, mixtures can be physically separated and a compound can only be separated by chemical means.
We reviewed Avogadro's Hypothesis on how two samples of gas at the same volume, temperature, and pressure contain the same number of molecules. The class revisited the Law of Definite Proportions and the law of Multiple Proportions. The Law of Definite proportions states a chemical compound always contains exactly the same proportion of elements by mass. The Law of Multiple Masses states when two elements combine with each other to form two or more compounds, the ratios of the masses of one element that combines with the fixed mass of the other are simple whole numbers.
The class also went over Dalton's model of the atom. Dalton's model states all matter must be composed of particles, and particles shape and motion depend on their state of matter.
Examples of white-boarded review

On Tuesday, we continued to review for the Unit 4 test. We completed Unit 4 Review and white-boarded it as a class. The biggest thing I needed to remember for the test was the diatomic elements. Dr. Finnan taught us the 7-Up trick and I remembered them.

Example of White-boarded review guide

On Wednesday we took the test. I am happy with my grade of 31/34. I am curious to know what I did wrong. I'll make sure I stop by after school to find out. After the test we got our Unit 5 objectives and Dr. Finnan explained how we would need to know them because they are important to the unit.

 

On Thursday we got new seats. I am excited to work with my new table mates. We completed the Relative Mass Activity and came to the conclusion that it is possible to count by weighing. However, there is a method to it. You first have to find the average weight of the object, like we did with the packing peanuts. You then find the weight of the container with the objects inside. After that you find the weight of just the container. Then you take the difference of the weight with the objects in the container, and just the container. This allows you to find the weight of just the objects. After finding this, you divide the weight of just the objects by the average you found earlier. This gives you the number of objects.

 

On Friday, class was shortened because of the pep rally. Since I was in band I had to leave early so I didn't complete any of Unit 5 Worksheet 1. I was informed by a fellow classmate that we didn't do much of it so I look forward to catching up on it on Monday.

I would also like to thank Dr. Finnan for collecting my ticket at Homecoming and I look forward to another great week in science.